A miscarriage can happen as early as the first week after a fertilized egg implants in the uterus, which is around the fourth or fifth week of pregnancy (counted from your last period). At that stage, most people don’t yet know they’re pregnant. The risk of loss is highest in these earliest weeks and drops significantly once a heartbeat is detected, typically around week six or seven.
The Earliest Losses: Chemical Pregnancies
The very earliest type of miscarriage is called a chemical pregnancy. This occurs within the first five weeks of pregnancy, before anything can be seen on an ultrasound. In a chemical pregnancy, the embryo implants briefly enough to trigger a positive pregnancy test by producing small amounts of the hormone hCG, but it stops developing almost immediately. Many chemical pregnancies happen so early that the only sign is a late period with slightly heavier bleeding than usual. Without a pregnancy test, most people would never know the pregnancy existed at all.
Chemical pregnancies are extremely common. They account for a large share of all pregnancy losses, though exact numbers are hard to pin down precisely because so many go undetected. The loss typically happens on its own within a few days and rarely requires any medical treatment.
How Risk Changes Week by Week
The risk of miscarriage is not spread evenly across pregnancy. It’s concentrated heavily in the first several weeks and falls off quickly. A large Australian study found the following pattern:
- Week 6: Risk of miscarriage is about 9.4%
- Week 7: Risk drops to about 4.2%
- Week 8: Risk falls to 1.5% and continues decreasing
By the time you reach 12 to 13 weeks, the risk is very low. Clinically, early pregnancy loss is defined as a nonviable pregnancy within the first 12 weeks and 6 days of gestation. After the first trimester, loss is much less common and is classified differently (as a late miscarriage or stillbirth depending on the stage).
The sharp drop between weeks six and eight is one reason many people wait until around 12 weeks to share pregnancy news. Once a heartbeat is confirmed on ultrasound, the odds shift dramatically in favor of the pregnancy continuing.
Why Early Miscarriages Happen
About 50% of all first-trimester miscarriages are caused by chromosomal abnormalities, meaning the embryo received the wrong number of chromosomes during fertilization. These are random errors in cell division that prevent the embryo from developing normally. They’re not caused by anything the mother did or didn’t do, and in most cases they can’t be predicted or prevented.
Other factors that can contribute to early loss include hormonal imbalances (particularly low progesterone), problems with the uterine lining that prevent proper implantation, thyroid disorders, uncontrolled diabetes, and certain immune system conditions. In many cases, especially with very early losses, no specific cause is ever identified.
Age and Miscarriage Risk
Maternal age is one of the strongest predictors of miscarriage risk, and the relationship is steep. A large study published in the BMJ found that the risk of miscarriage was lowest among women aged 25 to 29, at about 10%. After age 30, the risk climbs steadily. By age 45 and older, more than half of all pregnancies (53%) end in miscarriage.
This increase is driven primarily by egg quality. As eggs age, they become more prone to the chromosomal errors that cause most early losses. This doesn’t mean every pregnancy at 40 will end in miscarriage, but it does mean the statistical likelihood is higher, and very early losses in particular become more frequent.
What Early Miscarriage Feels Like
The physical experience of an early miscarriage depends heavily on how far along the pregnancy was. A chemical pregnancy at four or five weeks may feel like nothing more than a heavy, slightly late period. You might notice more cramping than usual and heavier bleeding for a few days.
A miscarriage between six and twelve weeks is more noticeable. Cramping can range from moderate to intense, and bleeding is typically heavier than a normal period. You may pass small clots or tissue. Once the process starts and cramping and bleeding begin, most of the tissue passes within a few hours. Light spotting or bleeding can continue for up to a month afterward.
One important warning sign: if you’re soaking through more than two large pads per hour for two or more hours, that level of bleeding needs immediate medical attention.
How Miscarriage Is Confirmed
In a healthy early pregnancy, hCG levels roughly double every 48 to 72 hours. When hCG levels fail to double, or when they start declining (for example, dropping from 120 to 80 over two days), it’s a sign the pregnancy is no longer developing. A slow rise, like 120 to 130 over two days, can also indicate a nonviable pregnancy.
Ultrasound provides more definitive answers. A gestational sac measuring 21 millimeters or larger with no visible embryo inside is considered diagnostic of a loss. Similarly, if an embryo measures 5 millimeters or more but shows no heartbeat, the pregnancy is nonviable. When early ultrasound results are uncertain, doctors will often repeat the scan seven or more days later. If the sac is still empty on that second scan, a loss is confirmed.
What Happens After an Early Loss
There are three main paths after an early miscarriage. With expectant management, you let the process happen naturally. This works best when cramping and bleeding have already started. Many people pass all the tissue on their own without any additional intervention.
Medication can speed the process when the body hasn’t started on its own. Cramping and bleeding typically begin within a few hours of taking the medication, and most people pass the tissue within 48 hours.
A minor procedure can also be used to remove the tissue, particularly if the other approaches are incomplete or if you prefer not to wait. Light spotting and cramping during and after the procedure are normal.
Your cycle typically returns within four to eight weeks after an early miscarriage. Ovulation can resume as soon as two weeks after a first-trimester loss, which means it’s physically possible to become pregnant again before your first period returns.